Increasing chain length of alkyl esters and alkyl ketones



United States atent Ofilice 3,086,982 Patented Apr. 23, 1963 This invention relates to the preparation of alkyl esters and alkyl ketones of relatively higher molecular weight from alkyl esters and alkyl ketones. In one of its aspects, the invention relates to increasing the chain length or molecular weight of an alkyl ester by effecting a reaction of it and a l-olefin having 412 carbon atoms in the molecule, said l-olefin being the sole essential olefinic material present, and a free radical generating dialkyl peroxide under conditions causing pyrolysis of said peroxide. In another of its aspects, the invention relates to the increase of the molecular Weight or chain length of an alkyl ketone by a reaction of it and a l-olefin and a dialkyl peroxide at a temperature causing pyrolysis of said peroxide and generation of free radicals therefrom.

It has been found that the pyrolysis of a dialkyl per oxide, containing a tertiary carbon atom attached to the oxygen of the peroxide functional group generates alkyl radicals which abstract 21 hydrogen from an alkyl group which can be attached to an ester and/ or to a ketone and that, if l-olefin is present, the olefin will enter the chain by addition to the new formed radical. Chain termination or transfer then completes the reaction. It has further been found that either of the alkyl chains or groups of the ester and/ or ketone molecule can be attacked by the radicals thus abstracting a hydrogen from either alkyl or chain, adding the olefin at either end of the molecule.

Esters are usually prepared by reaction between an organic acid and an alcohol. The alkyl chain lengths are determined by selecting the correct alcohol and acid. However, it is obvious that this method limits the esters which can be prepared by availability of alcohols and acids of the desired chain length. In many instances, the higher alcohols and some of the acids are not commercially available in quantity or in such a price range that these would be suitable for commercial exploitation. Similar discussion can be made in the case of the ketone.

It is an object of this invention to prepare alkyl esters and alkyl ketones having a relatively higher alkyl or chain length from readily available alkyl esters and/or alkyl ketones. It is another object of the invention to provide a method for increasing the chain length of aliphatic esters and/or ketones to a predetermined longer length.

Other aspects and objects of the invention are apparent from a study of this disclosure and the claims.

According to the present invention, there is provided a process for the preparation of a higher molecular weight ester and/or ketone from a relatively lower molecular weight alkyl ester and/or ketone which comprises reacting said ester and/or ketone in the presence of a l-olefin having 4-12 carbon atoms in the molecule and being the sole essential olefinic material present and a tertiary carbon atom containing dialkyl peroxide under conditions causing pyrolysis of said peroxide to generate free radicals.

Suitable esters for practicing the invention are the alkyl esters having an alkyl attached to the carbalkoxy group or substituted alkyl esters having an alkyl attached to the carbalkoxy group which are economical to use and readily available. Especially useful esters which are now preferred include Methyl valerate Ethyl valerate Ethyl isovalerate Methyl isovalerate Ethyl caprylate Methyl caprylate Ethyl palmitate Methyl acetate Ethyl acetate Methyl propionate Ethyl propionate Methyl butyrate Ethyl butyrate Ethyl isobutyrate and the like.

Other alkyl esters having up to 12 carbon atoms in either or both chains can be utilized.

Suitable ketones are the dialkyl ketones are substituted dialkyl ketones which are also economical to use and readily available. Especially useful ketones which are now preferred include Dimethyl ketone Diethyl ketone Methylethyl ketone These ketorles are available in commercial quantities. Other ketones having up to 12 carbon atoms in either or both chains can be utilized. It now appears that addition to the chain of higher molecular weight members of the ketone family, formed in the course of the reaction of the invention, contributes to the formation of some of the heavier members found in the reaction products.

Peroxides for the reaction of the invention include the following:

Di-tertiary-butyl-peroxide Di-tertiary-amyl-peroxide Bis-(triethylmethyl) peroxide Tertiary-butyl-pentamethylethyl peroxide Tertiary-butyl-triphenylmethyl peroxide Bis-(triphenylmethyl) peroxide The olefins which are used according to the invention are those having 4 to 12 carbon atoms in the molecule in which the double bond is in the 1 position.

It will be noted that the peroxides are dialkyl peroxides in which the total number of carbon atoms of the alkyl groups including the carbons of substituents in the alkyl groups is in the range 8 to 50 atoms.

EXAMPLE I A reaction of ethyl acetate 1352 g. (15.4 moles) with l-hexene 101 g. (1.2 moles) in the presence of tertiarybutyl peroxide 119 g. (0.081 mole) was effected in a silverlined reactor, which was slowly rocked for 44 hours at C. to agitate the liquid reactants.

Approximately 50 percent of the added l-hexene was converted to higher boiling products. These higher boiling products were characterized by mass, infrared and chemical means as follows:

Fraction Weight No. B.P., 0. Product percent of product 1 2 -230 C12 olcfins of various types 11 Ethyl caprylate i 8 Z-octyl acetate 4 n-Octyl acetate Trace 230 Ollfil'lS c1g 39 290 310 C1PSher 22 210-30/(1 mm... C22 ester; 16

1 Complete characterization of these esters has not been accomplished. Infrared indicates they are not acetate esters. Fraction No. 4 may therefore he CJII GOOGSH and/or CIEHZTGOGCEHI, and Fraction No. 5 may lit. OflI COOCMH CHHFCOOCBHU, and/or CmHz COOCzHs' Physical constants of these fractions are as follows;

a sence 1 Calculated [or fully saturated compounds.

Generally, the reaction time can be varied. A range of Table I DATA ON THE PRODUCTS FROM THE FREE RADICAL REACTION OF AGETUNE WITH l-HEXENE eiiluent charged to fractionation this hexenc-l represents approximately 34 percent unreacted.

The still residue (90.3 grams) represented the reaction products and was chromatographically separated into a benzene/methanoleluted cut and a cyclohexane-eluted cut. Upon subsequent fractional and vacuum distillations, the benzene/methanol-eluted cut was separated into four fractions and the cyclohexane-eluted cut was separated into two fractions. Subsequent examination indicated that the composition of six fractions was as postulated in Table I.

Bromine Moi. weight Molar retrae. Fraction number Other data No. B.I., C Postulated compound(s) nu (11 (sec footnotes) Calo Found 05110. Found 1 Cale. Found 7 191-2 0113000 11.. 0 1 142 140 5 1. 4218 i 0. s13 43. s 44. e 2, 3, 4, c, 181-6/60 mm CHaCOCmHgr-Hr. 0 7 226 230 1. 1421 0. S13 71. 5 72. 0 2, 3, (i. 154-60/(1 mm... CIi:GOCiu1Ir1)3o 0 15 310 309 1. 4533 0. 837 99. 2 101 2, 3, 6. {l/ 1 min CIIQCOCE51{H)51 (l 28 394 448 1. 4660 0. 862 127 127 2, 3, 6. 110-12/45 mm C olcflns 95 81 174 68 7. 6 215-/45 mm C1Hi3 isCOCiaHz 0 30 310 331 1 4552 0 p.28 99. 2 102 2, 3, 7.

1 Assuming saturated compounds except for Fraction 5.

2 Fractions 1, 2, 3, and 4 all give NallSO adducts and their infrared spectra contain a band at 8.6 characteristic of methyl ketones; Fraction 5 does not give a bisulfitc adduet nor does its infrared spectrum contain the 8.6 band.

B Semicarbazone and 2-4-dinitropheuylhydrnzone dreivatives prepared. All were OllS except those for Traction 1:

e For 2 nonanoue.

l Mass, inirared and gas chromatography confirm this compound to be almost pure (95+%) fl-nonanone.

6 Literature no, 1.4207; d 0.821.

' Fractions 1 to 4 were from the bcnzene/methanol-cluted out.

7 Fractions 5 and 6 were from the eyclohexanecluted cut.

from about 1 to 50 hours or more now appears to provide suificient time for an appreciable reaction to occur. Residual peroxide when present during the separation of the reaction products may lead to explosions if a distillation flask is taken nearly to dryness. Therefore, in the example, 44 hours were taken to make certain that the peroxide was completely pyrolyzed. The decomposition of peroxides by pyrolysis is not sensitive to pressure; therefore, essentially the vapor pressure of the reactants constitutes the lower limit on this variable. Inert gas can be used to pressurize the reactor, if desired. The reaction temperature is preferably maintained in the range 100 to 150 C. Since the half-life of the peroxide is temperature-sensitive, the reaction time ordinarily will be varied inversely with the temperature. The mole ratio of ester to olefin should be in the range 2 to 20, which is now preferred, although beneficial results can be obtained by operating with ratios above 20. It is possible to operate below a ratio of 2. The latter ratio favors the formation of polymer and, therefore, is not now recommended. A ratio above 20 decreases the yield per pass, but tends to improve product quality and overall yield based on olefin charged.

EXAMPLE II To a closed and heated, silver-lined steel reactor were added 1189 grams acetone, 115 grams l-hexene, and 11.9 grams of tertiary-butyl peroxide. The temperature was maintained at 125 C. and the reactants were agitated by placing the reactor on a rocker mechanism. After 48 hours, the reaction products were cooled and removed from the reactor.

Of the reactor efliuent a 1084.3 grams (82.5 weight percent) batch was subjected to distillation. A low boiling (54 to 80 C.) fraction weighed 994 grams and contained approximately 28 grams or 24 weight percent of the charged hexene-l. On the basis of the amount of The general discussion preceding the last example applies to the reaction of the invention with ketones. However, although ratios as low as l of ketone to 1 of olefin can be employed under certain controlled conditions, it is now preferred that the mole ratio of ketone to olefin be in the range of about 10 to 50. As in the case of the esters, the reaction time is sufiiciently extended for purposes of safety to permit complete decomposition of the peroxide which has a half life of approximately 4 hours at about C. A reaction time of 1 hour would give reasonably acceptable yields and, indeed, would be now preferred for commercial installation in which complete decomposition of the peroxide may not be necessary or could be accomplished without having to continue the reaction for a time extended, as in the foregoing example.

Generally, the invention is one in which the reactions take place in liquid phase which is advantageous, as one skilled in the art in possession of this disclosure will appreciate. Liquid phase reactions are more readily controlled, are less dangerous and to be preferred over high pressure gas or vapor phase reactions for obvious reasons. However, since the peroxides of the present invention are not sensitive to moderate pressures, it is possible according to the invention, for example, in removing product or the like, to pressurize the reactor with an inert gas.

The result of careful analysis of the products from the novel process of this invention indicate that the following reactions probably are principally responsible for the desired products.

R Bi

In the foregoing, the Rs can be as follows:

R, can be methyl, ethyl, tertiary butyl, phenyl, tolyl, naphthyl or biphenylyl.

R can be methyl, ethyl, tertiary butyl, phenyl, tolyl, naphthyl or biphenylyl.

R can be hydrogen, methyl, ethyl, tertiary butyl, phenyl, tolyl, naphthyl or biphenylyl.

R, can be alkyi with 1 to 12 carbon atoms or hydrogen.

R can be alkyl with 1 to 12 carbon atoms.

R can be alkyl with 1 to 12 carbon atoms.

R; can be ailtyl with 1 to 12 carbon atoms.

R can be alkyl with 4 to 12 carbon atoms.

Reasonable variation and modification are possible within the scope of the foregoing disclosure and the appended claims to the invention the essence of which is that tertiary carbon atom containing dialltyl peroxides and l-olefins are used to increase the alkyl group or chain length of an ester and/or a ketone under conditions causing pyrolysis of the dialkyl peroxides.

I claim: 1

1. A method for increasing the chain length of the alkyl group of a compound selected from the group consisting of alkyl esters having an alkyl attached to the carbalkoxy group having at least 3 carbon atoms and dialkyl ketones which comprises reacting at least one of said esters and ketones and a monomeric l-olefin having 4-12 carbon atoms to the molecule and the double bond in the 1 position as the sole essential olefinic starting material present and a free radical generating tertiary carbon atom containing dialkyl peroxide having in the alkyls a total of 8-50 carbon atoms substantially in the liquid phase at a temperature in the range 100-150 C. at which pyrolysis of said dialkyl peroxide occurs, the mol ratio of ester to l-olefin monomer being greater than 2 when ester is present and the mol ratio of ketone to l-olefin monomer being at least when ketone is present, selecting within said mol ratio ranges, a ratio providing a condition under which polymerization of, the l-olefin is substantially discouraged.

2. A process for increasing the chain length of an alkyl group in an alkyl ester having an alkyl attached to the carbalkoxy group which comprises reacting said ester having at least 3 carbon atoms and a monomeric l-olefin having 4-12 carbon atoms in the molecule and the double bond in the 1 position as the sole essential olefinc starting material present and a free radical generating tertiary carbon atom containing dialkyl alkyls a total of 8-50 carbon liquid phase at a temperature in the range -150 C.

peroxide having in the atoms substantially in the at which pyrolysis of said dialkyl peroxide occurs, the mol ratio of ester to l-olefin monomer being greater than 2 and of a value such that polymerization of the l-olefin is substantially discouraged.

3. A process for increasing the chain length of an alkyl group of a dialkyl ketone which comprises reacting said ketone and a monomeric l-olefin having 4-12 carbon atoms to the molecule and the double bond in the 1 position as the sole essential olefinc starting material present and a free radical generating tertiary carbon atom containing dialkyl peroxide having in the alkyls a total of 8-50 carbon atoms substantially in the liquid phase at a temperature in the range 100-150 C. at which pyrolysis of said dialkyl peroxide occurs, the mol ratio of lcetone to l-olefin monomer being at least 10 and of a value such that polymerization of the l-olefin is substantially discouraged.

4. A process for preparing an aliphatic ester having at least 7 carbon atoms in an alkyl group which comprises reacting ethyl acetate, monomeric l-hexene as the sole essential olefinic starting material present and free radical generating tertiary-butyl peroxide substantially in the liquid phase at a temperature of approximately C. for a time suilicient to cause appreciable reaction to occur, the mol ratio of the ethyl acetate to l-nexane being of a value such but always in excess of two that polymerization of the l-hexene is substantially discouraged.

5. A process for the preparation of a ketone having at least 7 carbon atoms in an alkyl group which comprises reacting acetone, monomeric l-hexene as the sole essential olefinic starting material present and free radical generating tertiary-butyl peroxide substantially in the liquid phase at a temperature of about 125 C. for a time sutlicient to allow appreciable reaction to occur, the mol ratio of the acetone to l-hexene being of a value such but always at least ten that polymerization of the l-olefin is substantially discouraged.

6. A method for increasing the chain length of the alkyl group of a compound selected from the group consisting ofi alkyl esters having an alkyl attached to the carbalkoxy group having at least 3 carbon atoms, having a total of 1 to 24 carbon atoms in the alkyls, and dialkyl ketones, having a total of 1-12 carbon atoms in the alkyls, which comprises reacting at least one of said esters and kctones and a monomeric l-olefin having 4-12 carbon atoms to the molecule and the double bond in the 1 position as the sole essential olefinic starting material present and a free radical generating tertiary carbon atom containing dialkyl peroxide, having a total of 8 to 50 carbon atoms in the alkyls, at a temperature in the range 100-150 C. substantially in the liquid phase at which pyrolysis of said dialkyl peroxide occurs, the mol ratio of ester to l-olefin monomer being greater than 2 when ester is present and the mol ratio of ketone to l-olefin monomer being at least 10 when ketone is present, selecting within said mol ratio ranges, a ratio providing a condition under which polymerization of the l-olefin is substantially discouraged, the mol ratio of the acetone to 1-hexene being of a value such but always at least ten that polymerization of the l-olefin is substantially dis- 'couraged.

References Cited in the file of this patent UNITED STATES PATENTS 2,093,695 Larson Sept. 21, 1937 2,402,137 Hanford June 18, 1946 2,432,287 Cramer Dec. 9, 1947 2,551,643 Seger et al May 8, 1951 OTHER REFERENCES Urny et al.: Journal of American Chemical Society, vol. 75, pp. 4876 and 4877. October 5, 1953. 

1. A METHOD FOR INCREASING THE CHAIN LENGTH OF THE ALKYL GROUP OF A COMPOUND SELECTED FROM THE GROUP CONSISTING OF ALKYL ESTERS HAVING AN ALKYL ATTACHED TO THE CARBALKOXY GROUP HAVING AT LEAST 3 CARBON ATOMS AND DIALKYL KETONES WHICH COMPRISES REACTING AT LEAST ONE OF SAID ESTERS AND KETONES AND A MONOMERIC 1-OLEFIN HAVING 4-12 CARBON ATOMS TO THE MOLECULE AND THE DOUBLE BOND IN THE 1 POSITION AS THE SOLE ESSENTIAL OLEFINIC STARTING MATERIAL PRESENT AND A FREE RADICAL GENERATING TERTIRAY CARBON ATOM CONTAINING DIALKYL PEROXIDE HAVING IN THE ALKYLS A TOTAL OF 8-50 CARBON ATOMS SUBSTANTIALLY IN THE LIQUID PHASE AT A TEMPERATURE IN THE RANGE 100-150* C. AT WHICH PYROLYSIS OF SAID DIALKYL PEROXIDE OCCURS, THE MOL RATIO OF ESTER TO 1-OLEFIN MONOMER BEING GREATER THAN 2 WHEN ESTER IS PRESENT AND THE MOL RATIO OF KETONE TO 1-OLEFIN MONOMER BEING AT LEAST 10 WHEN KETONE IS PRESENT, SELECTING WITHIN SAID MOL RATIO RANGES, A RATIO PROVIDING A CONDITIONS UNDER WHICH POLYMERIZATION OF THE 1 -OLEFIN IS SUBSTANTIALLY DISCOURAGED. 